This invention relates to a method for the control of weed pests using the trimethylsulfonium salt of N-phosphonomethylglycine, a known herbicide.
N-Phosphonomethylglycine and agriculturally acceptable salts thereof are known to be effective herbicides for post-emergent control of various weed species, particularly annual and perennial grasses.
The N-phosphonomethylglycines, and certain soluble salts thereof, can be made in a number of different ways. One such method, as described in U.S. Pat. No. 3,160,632 (Toy et al., Dec. 8, 1964) is to react N-phosphinomethylglycine (glycinemethylenephosphinic acid) with mercuric chloride in a water solvent at reflux temperature, and subsequently separating the reaction products. Other methods include the phosphonomethylation of glycine and the reaction of ethyl glycinate with formaldehyde and diethylphosphite. The latter method is described in U.S. Pat. No. 3,799,758 (Franz, Mar. 26, 1974). In addition, there is a whole series of patents relating to N-phosphonomethylglycines, their salts and derivatives thereof, described as being useful herbicides and plant growth regulators. Such additional patents relating to the N-phosphonomethylglycine, methods of application, methods of preparation, salts, and derivatives, include U.S. Pat. No. 3,868,407, U.S. Pat. No. 4,197,254 and U.S. Pat. No. 4,199,354, among others.
The N-phosphonomethylglycines and agriculturally acceptable salts thereof are known to be quite effective in the post-emergent application to weed pests; however, when these compounds are applied in a preemergent manner, it is known that they are tightly bound to the soil and have essentially no pre-emergent activity at nominal rates.
By the term "post-emergent" as used herein, is meant the application of the herbicide to weed pests, after these pests have emerged from the soil. By "pre-emergent" is meant application of the herbicide compound to the soil (PES) or in the soil (PPI) prior to the emergence of the weed pests from the soil as a consequence of growth.